A smart grid delivers electricity from suppliers to customers using digital technology to save energy. This technology should also help to decrease peak demands of power, increase reliability and help to control voltage levels according to loads variations.
Smart grid (also called: Smart Electric Grid, Smart Power Grid, Intelligent Grid, IntelliGrid, FutureGrid, Intergrid, Intragrid etc.), need more information to enable to operate the control means like additional windings of transformers used to change voltage levels, circuit breakers used to connect/disconnect loads or make by-pass connections to increase power supply from under loaded lines to overloaded lines in the network and vise-versa when load decreases.
Generators in electric utilities, generate current at medium voltage to transmission transformers. They raise the voltage to very high levels. All over the length of the transmission long lines, power substations, with their distribution transformers, transform the voltage back into medium voltages supplied to the industrial areas and residential quarters in the cities.
Control teams and control equipment in utilities and substations, has good information and measured data about voltages and currents of both sides of the distribution transformers (incoming and out going lines. Each line includes usually 3 phases). But there is always a lack of information at the splitting points of transmission lines where there is more than one substation connected on the line. There is also a lack of information about the currents at the splitting points off the outgoing lines of the distribution transformers, feeding large number of secondary lines in urban areas.
The problem is even bigger at urban areas where low voltage lines supply electric power to small businesses and residents and many customers are connected to branches of the same power line, and they depends each other in their power consumption influencing their mutual voltage levels. The control systems cannot detect such local variations in current and voltage levels usually compensated by other branches of the line. They can see only the total current and voltage levels outgoing from the substations. In case that there is a big increase in current of a branch of a line, due to overloading with its voltage drop associated (and probably a temperature limits excess problem), when in the same time there is a small power consumption in neighborhood line branches, the control team can not detect any problem.
Another problem of the electric grid control is to detect rapidly an outage and its location. It is hard to know, especially in bad weather conditions in winter and/or at night that one or more lines are ruptured (fallen trees on electric lines, electric towers prostrated by inundation etc.).
The lack of information about the current distribution in local networks results in lack of control means. It happens very often that in such places power consumption is very high during some working hours of businesses, during the day, and very low at night. As a result there is a big drop in voltage during the working hours and too high voltage levels at night. Usually customers complains enable to detect such areas, but there is no means to control such phenomenon but a costly change in the network configuration, because the power control center usually has no on line information about these load changes to enable smart power back-up switching.
Actual smart grid developments enable to improve the current and voltage curves, to decrease instant peaks, improve cosine cp and eliminate some kinds of perturbations on power supply lines. These Smart Grid systems also regulate the network by decrease of power consumption at peak hours (with the aide of lower tariffs at other hours of the day, which is usually called dynamic pricing). Utilities encourage customers to install and use programmable thermostats with automated settings by offering dynamic pricing to shave peak loads. This rebate helps to change customer's behavior to approve demand response. Actual existing Smart Grid load control measurement means have only the indications of the out going currents from substations and the customer's current consumption where digital smart power meters are installed. But there is no information on currents distribution in the network between the end users and the outputs of the substations to enable real and better load control and voltage level regulation.
To address these problems and to provide more efficient load management and outage detection improved smart grids are required.
It is an object of the present invention to provide a system which is capable of providing information about the currents at the splitting points off the outgoing lines, especially of the distribution transformers, feeding large number of secondary lines in urban areas.
It is another object of the present invention to provide a system for rapidly detecting an outage and its location.
Other objects and advantages of the invention will become apparent as the description proceeds.